German Patent Application No. DE 196 45 944 A1 shows a control unit for a vehicle electrical system having at least two batteries, which are able to be loaded by a generator, and which are used for supplying various users. Information is fed to the control unit and consequently also to the microcontroller contained in it via various connections. The control unit and the microcontroller contained in it are able to output control signals via other connections. As a function of specifiable data, the vehicle electrical system control unit opens or closes the connection between the two batteries, and goes into a sleep mode after switching off. In this context, for the wake-up from the sleep mode, a field effect transistor is patched through for putting into operation the control unit by supplying a signal.
Control units like the vehicle electrical system control unit just described are, generally, sent into a standby mode or a sleep mode based on the no-signal current requirements, or rather their no-signal current consumption, when it happens not to be needed, or rather, is not being used. This applies to all control units, just as, for instance, to the vehicle electrical system control unit or comfort control units or peripheral control units in particular in a vehicle, which do not have to execute an uninterrupted processing of tasks with respect to their function. This also applies, for instance, to control units in locking systems, control units which drive servomotors such as, for example, for window lifters or a sunroof, or even an outer mirror adjustment.
All these control units which are intermittently able to be put into standby mode or sleep mode, independent of whether they are being used in the vehicle or elsewhere, are cyclically activated in a sort of polling operation. This applies to the controller, as well as parts of the periphery. It thereby becomes possible, during these active phases, to record time-critical and other external events and signals, such as switching positions. Depending on that, the entire control unit is then activated anew or remains in sleep mode or standy mode. This method leads to a high current consumption of the control unit.
If, for example, several control units are simultaneously activated in this way, then for each control unit only a certain part of the overall available energy or current is usable. In this manner, either not many control units are able to be operated simultaneously like this, or attempts are made to solve the problem, in that very large scanning times, that is, cycle times, are selected between two activity phases.
Thus, the related art has not been able to yield optimum results in all regards.